Writer: Norman Martin
CLOVIS - Most of the state's dairies use high-energy corn silage or feed to bulk up their milk cows. But the economic glitch has been that corn is a water hog when it's growing under New Mexico's blistering sunshine, needing slightly under a yard of water a season to produce a good crop.
A New Mexico State University scientist is investigating a way to slice that irrigation water use by a third simply by shifting from corn to forage sorghums.
"The underground water resources that we use for irrigation here in eastern New Mexico are limited," said Mark Marsalis, an agronomy specialist at NMSU's Agricultural Science Center at Clovis. "Pumping large amounts of water to produce high-yielding corn silage is not sustainable."
Last spring the researcher began a limited irrigation study comparing yield and nutrient value among two types of forage sorghum and corn. The four-acre experimental plots at the 164-acre Clovis science center, located 15 miles north of Clovis on State Road 288, uses a center pivot irrigation system to water the crops.
"In the first growing season, both forage sorghums out-yielded the corn on a tonnage per inch of irrigation water basis," Marsalis said. "But we're still looking at the quality data."
Marsalis emphasized that the study was not a variety test comparing individual yields. Rather it was how well the sorghums and corn performed with minimal water. The goal is to find a forage crop that can be just as productive as corn, while using less water, he said.
Limited irrigation translated into about 20 inches of water spaced over a 120-day growing period. Typically, corn will need about 30 inches of water to produce a decent crop.
Today, the dairy feed of choice in New Mexico is corn, while forage sorghums are only used sporadically. But saving just a little on production costs by moving to the forage sorghums could have major economic benefits because of the large volume involved.
New Mexico is the nation's fastest-growing milk-producing state. It ranks seventh nationally in dairy product sales, with dairies adding more than $730 million to the state's economy. New Mexico has about 180 dairies and some 326,000 head of dairy cattle.
One factor driving this growth has been the excellent environmental conditions, especially on New Mexico's eastern side near Clovis and Portales. Indeed, Curry, Roosevelt and Chaves counties alone account for over 63 percent of the state's milk cow numbers and cash receipts.
But, as with much of the Southwest, water availability for irrigation is and will continue to be a limiting factor. It's one reason why Marsalis chose forage sorghums. Their nutritive value, yield potential and water-use efficiency are excellent, he said.
In the field, forage sorghums are quite distinctive. Normally, grain sorghums are about waist high. Forage sorghums range between 7- to 15-feet tall and can produce the large tonnage dairies require.
Another aspect to the NMSU project is an ensiling component, which will investigate the potential of adding a cheese whey dairy industry byproduct to silage for quality improvement.
When harvesting silage material, the entire above-ground part of the plant - leaves, stem and grain - is chopped and placed in a silo or pit for later use as a feed. Using compaction pressure, the oxygen is removed and the compacted material is preserved as a livestock silage.
"This phase of the experiment has both economic and environmental implications since the byproduct is one that must be disposed of somehow," Marsalis said.
This winter Marsalis will continue examining the long-term quality of the ensiling feed, as well as the yield data from the experimental plots. "Our goal is to help farmers better determine the tradeoff from an economic and resource conservation perspective," he said.
© 2013 New Mexico State University Board of Regents
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